Biosensing of hydrogen peroxide was made at a carbon paste electrode incorporating fumed silica, horseradish peroxidase and N-methyl phenazine methosulphate. Cyclic voltammetric and amperometric measurements were used for the first time to demonstrate the suitability of electron communication between horseradish peroxidase and a carbon paste electrode via N-methyl phenazine methosulphate, an electron transfer mediator. Performance and characteristics of the biosensor were evaluated with respect to response time, detection limit, applied potential and concentration of the mediator. Effect of applied potential and amount of the mediator in carbon paste on the Michaelis-Menten constant of the biosensor was investigated. The biosensor possessed a variety of characteristics including long stability and rapid response and high sensitivity to hydrogen peroxide, with a detection limit of 0.08 μM.